1. Field of the Invention
The present invention relates to a support and introduction bench for an elongated rectilinear probe, of the type used for carrying out samplings in smelting-reducing furnaces such as blast furnaces. The invention further relates to a probe adapted to be used with such a bench.
2. Description of the Related Art
Benches are generally known and used in apparatuses for probing through an orifice provided in the wall of the furnace. Such probing apparatuses normally include means for tightening and/or guiding the probe, which are joined to the furnace wall, as well as means for introducing the probe. Often, the probe is introduced into the furnace by exerting a thrust force at the level of its rear end.
In certain cases, the probes can be very long and have a small diameter (for example 13 m long for 90 mm diameter) thus it is important for the probes to be supported between the guiding device close to the furnace and the introduction device, in order to prevent bending. To this effect, there has been is provided substantially in the axis of the introduction orifice made in the wall of the furnace, a bench of length adapted to the length of the probes and equipped with means for driving the probe according to a translatory movement along its axis, as well as support and guide means distributed along the length of the bench.
A bench of this type is described in patent document FR-2 472 018. According to this document, the bench is composed of a frame forming two parallel rails for guiding a probe-holding carriage which holds the rear end of the probe and which is designed to drive it according to a translatory movement and to transmit thereto the force necessary to its penetration into the furnace. The carriage itself is moved by means of chains connected to a driving member and comprises driving rollers which are engageable in the guide rails of U-shaped cross-section. Support and guide arms designed to prevent or limit any bending and buckling of the probe, are secured at regular intervals on the bench and their ends, situated above the probe, comprise guiding clamps encircling the probe. Said clamps have a part which is fixed with respect to the arm, and another part which is articulated thereon and which is pivotable upward to allow positioning of the probe on the bench. A free space is provided between the lower ends of the two parts of the clamp to allow the passage of the lugs securing the probe on the carriage during the translatory movement of the latter.
The securing lugs provided on the probe are therefore relatively thin and extend on only one side of it in order to be connected on fastening brackets provided on the carriage.
The probe axis is then offset upwardly with respect to the horizontal median plane of the carriage, hence with respect to the median plane of the carriage guide rails.
It has been found that, although this disposition may be suitable when the probe penetration force is low, it presents on the other hand, serious disadvantages as soon as the resistance to the penetration increases. Indeed, due to the position of the probe axis above the horizontal median plane of the guide rails and of the offset position of the probe with respect to the point of application of the pulling force exerted by the chains on the carriage, resistance of the probe to penetration causes a tilting moment for the carriage, which tends to raise its front part, and which creates a bracing of said carriage in the rails, thereby increasing the friction and tending to draw the flanges of the guide rails apart and to deform them.
As a result, the probe end which is held on the carriage also tends to move angularly from the theoretical axis of penetration, this contributing to causing buckling which in turn tends to increase the bracing phenomenon. This problem is further emphasized by the play which exists between the rollers of the carriage and the rail.
In addition, the guide arms are permanently situated above the probe and interfere with the positioning of said probe on the bench. Moreover, the clamps only grip the probe laterally at two diametrically opposite points of the probe, without forming an abutment above it, buckling tends to bend the probe upwardly, and hence to jam it between the two parts of the clamps.
To understand the importance of the arising problems, it should be noted that in the case of a probe of 90 mm diameter, the force required to introduce it inside a blast furnace can reach 80 kN, and for a sampling probe of 300 mm diameter, the force is near 250 kN.